1. Field of the invention
The present invention relates to a wide-field exposure optical system which can perform a wide-field and high resolution projection.
2. Description of Background Art
There has been known as a high resolution projection apparatus in the prior art a stepper which has a lens optical system and sequentially projects onto subdivided light-receiving objects and then exposes them. Such a stepper can perform the scaling (i.e. minification and enlargement) and also can increase the numerical aperture (NA).
However when trying to obtain the wide-field the magnification of projection becomes 1 (one) and the abaxial aberration is caused. It is difficult to correct these problems and therefore it is difficult, for example, to obtain a field more than 15.times.15 cm.sup.2.
It is also known other high resolution projection apparatus of the prior art such as disclosed in Japanese Patent Publication No. 51083/1982. This projection apparatus is a scanning type apparatus in which a concave mirror 100 and a convex mirror 102 are oppositely arranged as shown in FIG. 5.
In this optical system, an object to be projected and an imaging position are arranged at a symmetric position centered on an optical axis 104 and an aberration corrected region 106 is formed in an annular region centered on the optical axis 104. The luminous flux used in projection is only a luminous flux which transmits through the aberration corrected region limited by a mask (not shown) arranged near both the object to be projected and the imagery position. The scanning is performed by moving the object to be projected and a photosensitive material arranged at the imaging position with synchronizing them with each other along arrows shown.